1. Field of the Invention
This invention relates to a rolling bearing unit that is desirably used in a location where there is high-speed minute rocking motion, such as for use in the swing arm of a magnetic disk apparatus.
2. Description of the Related Art
In a prior art rolling bearing unit for a swing arm, in the case of 3.5 xe2x80x9cHDDxe2x80x9d as shown in FIG. 15, ball bearings 100 with a grease sealed in them are used under a specified pre-load. An E block 200 is integrally formed with a swing arm or swing arms. As to the E block 200, mainly used are a pulling type in which a single bolt 400 is screwed into the central portion of the housing 300 for bolt-fastening, and an adhesion type, not shown in the figures, in which the outer-diameter side 301 of the housing 300 is adhesion-fixed to the inner peripheral surface of the E block 200.
In addition, mainly used in the case of 2.5 xe2x80x9cHDDxe2x80x9d as shown in FIG. 16 is an integration type which comprises press-formed flat plates 201 and spacers 500 each provided between a pair of the flat plates 201, which are fixed to the housing 300 between a flange portion of the housing 300 and a nut 600.
Recently, there is an increasing demand for higher density magnetic disk devices. In order to accomplish this, the track width on which signals are recorded on the disk have become increasingly more narrow, and there is a demand that the swing arm(s) installed in the head for reproducing the signals be capable of accessing the target track at high-speed and with highly precise positioning. A method of clamping a couple of disks for the pivot is developed in order to satisfy the demand, without using the housing.
Conventionally, as shown in FIG. 15, the housing 300 is pulled via the bolt 400 toward the E block 200 side at one location in the center of the outer-diameter side of the housing 300, so that the E block 200 is clamped through contact between the housing 300 and E block 200, which needs the member for the housing 300 and expensive.
In the case of the integration type shown in FIG. 16 where the arm 200 is directly mounted to the housing 300, flange processing or screw processing is required for the housing 300, which is expensive.
Taking the above problems with the prior art into consideration, an object of this invention is to provide a rolling bearing unit that does not use the housing to reduce the number of parts, and in which the are is precisely fixed to the pivot.